Various devices including a smartphone, a tablet PC, and the like requiring M2M (machine-to-machine) communication and high data throughput and technologies are emerging and diffusing. Hence, an amount of data required to be processed in a cellular network is rapidly increasing. In order to satisfy the rapidly increasing data process requirements, a carrier aggregation technique for efficiently using more frequency bands, a cognitive radio technology, a multi-antenna technology for increasing data capacity transmitted in a limitative frequency, a multi-base station cooperative technology, and the like are developing. Moreover, a communication environment is evolving into a way that a density of a node capable of being accessed by a neighboring device is increasing. A node corresponds to a fixed point equipped with one or more antennas to transceive a radio signal with a user device. If a communication system is equipped with a node of high density, the communication system can provide a user device with a communication service of better performance via cooperation between nodes.
A multi-node cooperative communication system performs communication with a user device using the same time-frequency resource in a plurality of nodes. In the multi-node cooperative communication system, since each node operates as an independent base station, the multi-node cooperative communication system has significantly better performance in processing data compared to a legacy communication that performs communication with a user device without mutual cooperation.
The multi-node system performs cooperative communication using a plurality of nodes each of which operates as a base station, an access point, an antenna, an antenna group, a radio remote header (RRH), or a radio remote unit (RRU). Unlike a legacy centralized antenna system that antennas are located in a manner of being concentrated on a base station, in general, a plurality of the nodes are located in a manner of being apart from each other in the multi-node system. One or more base stations or a base station controller can manage a plurality of the nodes to control an operation of each node or schedule data to be transmitted/received by each node. A node is connected with the base station or the base station controller controlling the node via a cable or a dedicated line.
Since the multi-node system is able to communicate with a single user device or a plurality of user devices in a manner that distributed nodes transmit/receive a different stream at the same time, the multi-node system can be regarded as a sort of MIMO (multiple input multiple output) system. However, since the multi-node system transmits a signal using nodes distributed to various positions, a transmission area to be covered by each antenna is reduced compared to antennas installed in the legacy centralized antenna system. Hence, compared to the legacy system used to implement MIMO technique in the centralized antenna system, transmit power for transmitting a signal transmitted by each antenna can be decreased in the multi-node system. And, since a transmission distance between an antenna and a user device is shortened, path loss is reduced and fast transmission of data is enabled. In doing so, transmission capacity and power efficiency of a cellular system can be enhanced and communication performance of uniform quality can be satisfied irrespective of a position of a user device in a cell. Moreover, since the base station(s) and the base station controller(s) connected with a plurality of the nodes are participating in transmitting/receiving data in the multi-node system, a signal loss can be reduced in a transmission process. If nodes apart from each other as much as a prescribed distance perform cooperative communication with a user device, correlation and interference are reduced between antennas. In particular, it may be able to obtain high SINR (signal to interference-plus-noise ratio) through the multi-node cooperative communication system.
Because of the merits of the multi-node system, a next generation mobile communication system uses the multi-node system together with the legacy centralized antenna system or uses the multi-node system instead of the legacy centralized antenna system not only to reduce base station expansion cost and maintenance cost of a backhaul network but also to increase service coverage, channel capacity, and SINR.